1. Field of the Invention
The invention relates to a control apparatus and method that controls vehicle behavior.
2. Description of the Related Art
Japanese Utility Model Application Publication No. 5-13878 (JP-U-5-13878) and Japanese Patent Application Publication No. 2005-80902 (JP-A-2005-80902), for example, propose vehicle behavior control apparatuses that control the behavior of a vehicle in at least one rotational direction, i.e., the yaw direction, the roll direction, and the pitch direction, of the vehicle using a gyro-moment. The vehicle behavior control apparatus (in a vehicle with a flywheel) described in JP-U-5-13878 includes a flywheel that rotates about a horizontal axis in the length direction of the vehicle, first driving means for rotatably driving the flywheel about that horizontal axis, i.e., in the roll direction, and second driving means for rotatably driving the flywheel about a horizontal axis in the width direction of the vehicle, i.e., in the pitch direction.
With the vehicle behavior control apparatus described in JP-U-5-13878, a gyro-moment in the yaw direction, i.e., about a vertical axis in the height direction of the vehicle, is generated by rotating the flywheel in the pitch direction using the second driving means while rotating the flywheel in the roll direction using the first driving means. Accordingly, the control apparatus controls the behavior of the vehicle in the yaw direction, such as understeer and oversteer, by applying a gyro-moment generated in the yaw direction to the vehicle.
Also, the vehicle behavior control apparatus in JP-A-2005-80902 includes a flywheel that rotates about a vertical axis in the height direction of the vehicle, first driving means for rotatably driving the flywheel about that vertical axis, i.e., in the yaw direction, and second driving means for rotatably driving the flywheel about a horizontal axis in the length direction of the vehicle, i.e., in the roll direction. This control apparatus generates a gyro-moment about a horizontal axis in the width direction of the vehicle, i.e., in the pitch direction. Accordingly, the control apparatus controls the behavior of the vehicle in the pitch direction, such as nose dive and tail squat, by applying a gyro-moment generated in the pitch direction to the vehicle.
Noise, i.e., road noise and the like, increases as the vehicle speed increases. The noise from the rotation of a rotating body such as a flywheel increases as the rotation speed of the rotating body increases. Accordingly, even if the vehicle is traveling at a low speed such that the amount of road noise and the like is low, if the rotating body is rotating at high speed, the noise generated by that rotation may be relatively loud. However, neither JP-U-5-13878 nor JP-A-2005-80902 makes any mention of performing vehicle behavior control taking noise into account.
Further, the behavior of the vehicle in a rotational direction typically changes more quickly as the vehicle speed increases. A vehicle moves, turns, and stops using frictional force generated between the road surface and the tires, i.e., using the gripping force of the tires. Here, the gripping force of the tires is nonlinear so the behavior of the vehicle in a rotational direction may change suddenly from an increase in vehicle speed. Therefore, in order to deal with an increase in the rate of change, or a sudden change, in vehicle behavior that accompanies an increase in vehicle speed, the control response to the behavior of the vehicle in a rotational direction must be improved. However, neither JP-U-5-13878 nor JP-A-2005-80902 makes any mention of controlling the rotation state taking control response into account.